Where's That Radioactive Sulfur Now? Possibly In Your Pants

The Fukushima Nuclear Power Plant before the disaster. Image via Wikipedia

When the news broke yesterday that a previously unreported type of fallout from Fukushima—radioactive sulfur—had reached the United States in late March, nearly all mainstream media reports made the claim that it poses no threat to the health of Americans. But none of them explained where the radioactive sulfur went.

And if you're a man, you may be interested to know that some miniscule portion of it could be in your testicles.

Scientists from the University of California San Diego have routinely monitored natural levels of radioactive sulfur in the atmosphere in La Jolla, California, since 2009. Radioactive sulfur is produced naturally in the stratosphere when gamma rays strike argon atoms, but very little of that radioactive sulfur reaches the lower atmosphere.

On March 28, the researchers recorded a spike in radioactive sulfur that they doubted could have come from the stratosphere:

On a normal day, (Antra) Priyadarshi sees between 180 and 475 sulfur-35 atoms as sulfates per cubic meter of air, but on the 28th, her team recorded about 1500. "No one has ever seen such a high percentage of the stratospheric air coming into the marine-bound layer," she says.

The researchers surmise the sulfur was produced when emergency workers at Fukushima flooded the nuclear plant's runaway reactors with seawater to cool the melting fuel rods. Neutrons emitted by the fuel rods struck chlorine atoms in the water, forming sulfur-35 that escaped from the plant in the form of steam.

Prevailing winds carried the sulfur toward California, the researchers contend. They estimate that only about 0.7 percent of the radioactive sulfur emitted at Fukushima reached the California coast.

The California Air Resources Board estimates that Californians inhale 10-50 liters of air per minute during normal activities ranging from sitting to running. A liter equals 0.001 cubic meters, meaning Californians may have inhaled only about 360 radioactive sulfur atoms on that day—or more.

Priyadarshi's co-author, Mark Thiemens, assuredThe Los Angeles Times that the levels observed pose no threat to Californians. "The levels we observed are in no way harmful in California," Thiemens said.

Sulfur-35 is a weak beta emitter. All but 20 percent of the radiation it emits is halted by the dead layer of skin at the surface of the human body, according to the Health Physics Society. However, the body more readily absorbs ingested or inhaled sulfur.

Sulfur-35 has a half-life of 87.5 days outside of the body, but a biological half-life of 623 days, according to Michigan State University's Office of Radiation, Chemical & Biological Safety.

Most universities advise employees to handle volatile Sulfur-35 within a hooded enclosure.

Sulfur-35 is absorbed by the entire body but is of particular concern to men because it tends to concentrate in the testicles, according to a Nuclide Safety Data Sheet from the University of North Carolina Charlotte. Beta radiation occurring there could damage neighboring cells.

The San Diego researchers published their findings Monday in the Publication of the National Academy of Sciences. Their report does not address the heath effects of radioactive sulfur, which they do not consider significant in this event, but it seeks to use the La Jolla data to derive the intensity of neutron radiation at Fukushima.

Scientists including Andreas Stohl of the Norwegian Institute for Air Research and Edward Morse of UC Berkeley questioned the reliability of those conclusions, according to published reports.